Optical modulators are used to electrically modulate a laser beam from a laser source for optical communication, scientific instruments and other instruments. One type of optical modulator includes a crystal (EO material) and a drive circuit that applies a driving voltage across the crystal. In this design, the laser beam is directed at the crystal. The voltage across the crystal changes the index of refraction of the crystal. The amount in which the index of refraction is changed is proportional to the amount of voltage applied to it. With this design, the crystal changes the optical path length of the laser beam through the crystal in accordance with the frequency of the driving voltage. Thus, a laser beam emerging from the crystal is modulated by the frequency of the driving voltage. The effective voltage applied to the eo crystal can be amplified by placing the eo crystal within a resonant cavity. However, the amplification only occurs at fixed resonant frequencies supported by the fixed cavity dimension. Therefore, most optical modulators with fixed cavity design have a very limited tuning range.